Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$70.93	11.301%	$78.9458	$78.95	$78.95	$78.90
Purchase #2	$69.80	3.635%	$72.3372	$72.34	$72.35	$72.30
Purchase #3	$179.40	11.146%	$199.3959	$199.40	$199.40	$199.40
Purchase #4	$175.48	9.467%	$192.0927	$192.09	$192.10	$192.10
Purchase #5	$167.95	6.746%	$179.2799	$179.28	$179.30	$179.30
Purchase #6	$212.62	13.567%	$241.4662	$241.47	$241.45	$241.50
Purchase #7	$156.86	3.313%	$162.0568	$162.06	$162.05	$162.10
7 purchase totals =	$1,033.04		$1,125.5745	$1,125.59	$1,125.60	$1,125.60